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Biomedical subjects

H Bergmann

Publications and source records attributed to H Bergmann.

At least 19 recordsLinked to original sources
PubMed2007

Gastric emptying of glucose solution and associated plasma concentrations of GLP-1, GIP, and PYY before and after fundoplication.

BACKGROUND: This study was designed to assess the relationship between gastric emptying of glucose solution and the ensuing plasma concentrations of glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and glucose-dependent insulinotropic polypeptide (GIP) in patients having undergone fundoplication for gastroesophageal reflux (GERD). SUBJECTS AND METHODS: In 10 male patients the emptying of 50% glucose solution was determined scintigraphically and its relationship with plasma glucose, GLP-1, PYY, and GIP concentrations was studied before and 3 months after fundoplication. RESULTS: In the first 30 min after glucose ingestion, emptying was significantly (p = 0.048) faster after fundoplication than before. Emptying and GLP-1 and GIP correlated: the faster the emptying during the first 30 min the greater the concentrations integrated over that period (p = 0.04; p = 0.01; p = 0.02). Emptying and PYY concentrations were unrelated. In the 120-180 min. period, blood glucose concentrations were lower the faster the emptying in the initial 30 min (p = 0.06) and the entire 50-min recording period (p = 0.03) had been. The GLP-1 concentrations integrated over the first 30 min correlated inversely with the integrated plasma glucose during the third hour after ingestion (p = 0.004). CONCLUSIONS: After fundoplication, gastric emptying may, if accelerated in its initial phases, give rise to greater and earlier increases in plasma glucose, GLP-1, and GIP concentrations and thus to reactive hypoglycemia.

Adult↗
PubMed2006

Evaluation of a new electromagnetic tracking system using a standardized assessment protocol.

This note uses a published protocol to evaluate a newly released 6 degrees of freedom electromagnetic tracking system (Aurora, Northern Digital Inc.). A practice for performance monitoring over time is also proposed. The protocol uses a machined base plate to measure relative error in position and orientation as well as the influence of metallic objects in the operating volume. Positional jitter (E(RMS)) was found to be 0.17 mm +/- 0.19 mm. A relative positional error of 0.25 mm +/- 0.22 mm at 50 mm offsets and 0.97 mm +/- 1.01 mm at 300 mm offsets was found. The mean of the relative rotation error was found to be 0.20 degrees +/- 0.14 degrees with respect to the axial and 0.91 degrees +/- 0.68 degrees for the longitudinal rotation. The most significant distortion caused by metallic objects is caused by 400-series stainless steel. A 9.4 mm maximum error occurred when the rod was closest to the emitter, 10 mm away. The improvement compared to older generations of the Aurora with respect to accuracy is substantial.

Austria↗
PubMed2006

Effects of essential oils from fennel (Foeniculi aetheroleum) and caraway (Carvi aetheroleum) in pigs.

The ban of antibiotics as a feed additive requires alternatives to stabilize the health and performance particularly of the young animals. Essential oils obtained from fennel seed (Foeniculi aetheroleum) and caraway seed (Carvi aetheroleum) were tested in diets for weaned piglets in comparison with either a diet without feed additive or with a combination of formic acid and copper (positive control). Four groups of sixteen piglets (live weight 7 kg, age 26 days) received diets without (1) or with supplements of 7.5 g formic acid + 160 mg Cu/kg (2), 100 mg fennel oil/kg (3) or 100 mg caraway oil/kg (4) during 3 weeks after weaning. In the subsequent 4 weeks, all piglets were fed a diet without these additions. Fennel oil contained almost 2/3 anethol, approximately 1/5 fenchon and the remaining part consisting of alpha + beta-pinen, limonen (p-mentha-1,8-dien) and estragol. In the caraway oil, half of the contents was represented by limonen and the other half by carvon. There were no piglet losses and only few cases of diarrhoea. The combination of formic acid and copper increased feed consumption by 27% and daily weight gain by 25%. There were no differences in the performance between the group fed fennel oil and the control without additives. Piglets fed caraway oil tended to consume less feed and to gain approximately 10% less. In feed choice experiments, pigs consumed the same two diets from two troughs with 50% of total feed amount, as expected. The diets containing fennel or caraway oils were consumed at less than 50%. If the diet contained 100 mg fennel oil/kg, the decrease of percentual feed intake was significant. The results of the feeding experiment and of the feed choice experiment question the classification of fennel and caraway oils as flavour additives or as 'appetite promoters' in diets for weaned piglets.

Animal Feed↗
PubMed2005

Fast DRR generation for 2D/3D registration.

We present a simple and rapid method for generation of perspective digitally rendered radiographs (DRR) for 2D/3D registration based on splat rendering. Suppression of discretization artefacts by means of computation of Gaussian footprints--which is a considerable computational burden in classical splat rendering--is replaced by stochastic motion of either the voxels in the volume to be rendered, or by simulation of a X-ray tube focal spot of finite size. The result is a simple and fast perspective rendering algorithm using only a small subset of voxels. Our method generates slightly blurred DRRs suitable for registration purposes at framerates of approximately 10 Hz when rendering volume images with a size of 30 MB on a standard PC.

Algorithms↗
PubMed2004

[Pitfalls and complications of elastic stable intramedullary nailing (ESIN) of femoral fractures in infancy].

BACKGROUND: The aim of this prospective study was to evaluate the intra- and postoperative problems as well as the complications of elastic stable intramedullary nailing (ESIN) of femur fractures in children. PATIENTS AND METHODS: 47 consecutive children, mean age 6 years, were reviewed clinically and radiologically until hardware removal and after this annually. Mean time of follow up was 37 months. RESULTS: Intraoperatively one cortex perforation and one displacement of a third fragment occurred. Two correction operations were necessary: In one case due to an implant displacement and in another case due to an unacceptable loss of reduction. There were no infections, non union, implant breakage, refracture or disturbance of growth. CONCLUSIONS: ESIN is a safe procedure in femoral shaft fractures of children. Most of the problems and complications can be avoided by a careful consideration of the indication and a correct operation technique.

Bone Nails↗
PubMed2003

Elastic stable intramedullary nailing of midclavicular fractures in athletes.

BACKGROUND: Intramedullary fixation of midclavicular fractures may be a better option than non-operative treatment for high performance/professional athletes because of the potential reduction in recovery time. OBJECTIVES: To evaluate the effectiveness of intramedullary fixation in high performance athletes and the time required to return to sporting activity. METHODS: Data were taken from a prospective study on intramedullary fixation techniques using the elastic stable Ti nail (TEN, Synthes) for the treatment of displaced midclavicular fractures, initiated in 1996. The patients in 12 cases were classified as high performance/professional athletes. These cases were used to evaluate the technique specifically in this population. Fractures were classified according to the Orthopaedic Trauma Association (OTA) system. Patients were evaluated before and after surgery for shoulder function and subjective pain. After the operation, radiological assessments documented fracture healing, and clinical outcomes scores were obtained. Time required to return to training and competition was documented. RESULTS: All fractures were transverse or oblique. Mean (SD) shoulder abduction increased from 36.3 (8) degrees before surgery to 154.2 (17) degrees afterwards (p<0.001). Mean subjective pain score using a visual analogue scale (0-100) decreased from 71.7 (18) points before surgery to 19.2 (6) points (p<0.001) three days after. There were no complications. Hospital stay averaged 2.9 (1) days. Mean delay to resumption of training was 5.9 (1) days, and to resumption of competition it was 16.8 (5) days. The mean Constant clinical outcomes score one year after hardware removal was 98.3 (2) points. CONCLUSIONS: Intramedullary fixation of displaced midclavicular fracture was successful in terms of clinical outcome and rapid resumption of sporting activities. This treatment should be offered to athletes as an alternative to non-operative treatment.

Adolescent↗
PubMed2002

Conceptional considerations for a German influenza pandemic preparedness plan.

A pandemic appearance of influenza A virus must be expected at any time. The limitations of health preserving and life-saving resources, which will inevitably be reached in the event of a pandemic, will be accompanied by ethical and possibly social conflicts, which can be lessened or resolved only through precautionary planning, clearly specified competencies and transparent decisions within a social consensus. In case of a shortage of vaccines and virostatic agents, decisions will have to be made with regard to the segment of the population that absolutely must be vaccinated. It is currently estimated that a (monovalent) vaccine developed for a new pandemic strain would only suffice for the single vaccination of approximately half of the German population after a year; only 10-14 million vaccine dosages would be available to provide basic immunization and single boosters to personnel required to maintain basic medical care and essential infrastructure after half a year. In the event of local influenza outbreaks, antiviral chemotherapeutic agents could be used to close the gap until a vaccine can become effective. Even if suitable influenza vaccines and virostatic agents are not sufficiently available at the start of a pandemic, it is still possible to at least prevent an outbreak of two of the most feared secondary infections that accompany influenza: pneumococcal pneumonia or meningitis and illnesses resulting from Haemophilus influenzae. Agreement still needs to be reached with manufacturers for guaranteeing the necessary vaccine production or ensuring that they have a sufficient stock to meet the minimum demand for antiviral agents and agents for symptomatic treatment.

Antiviral Agents↗
PubMed2002

Computer-enhanced stereoscopic vision in a head-mounted display for oral implant surgery.

We developed a head-mounted display (HMD) with integrated computer-generated stereoscopic projection of target structures and integrated it into visit, a specific oral implant planning and navigation software. The HMD is equipped with two miniature computer monitors that project computer-generated graphics stereoscopically into the optical path. Its position is tracked by the navigation system's optical tracker and target structures are displayed in their true position over the operation site. In order to test this system's accuracy and spatial perception of the viewer, five interforaminal implants in three dry human mandibles were planned with visit and executed using the stereoscopic projection through the HMD. The deviation between planned and achieved position of the implants was measured on corresponding computed tomography (CT) scan images recorded post-operatively. The deviation between planned and achieved implant position at the jaw crest was 0.57 +/- 0.49 mm measured from the lingual, and 0.58 +/- 0.4 mm measured from the buccal cortex. At the tip of the implants the deviation was 0.77 +/- 0.63 mm at the lingual and 0.79 +/- 0.71 mm at the buccal cortex. The mean angular deviation between planned and executed implant position was 3.55 +/- 2.07 degrees. The present in vitro experiment indicates that the concept of preoperative planning and transfer to the operative field by an HMD allows us to achieve an average precision within 1 mm (range up to 3 mm) of the implant position and within 3 degrees deviation for the implant inclination (range up to 10 degrees ). Control during the drilling procedure is significantly improved by stereoscopic vision through the HMD resulting in a more accurate inclination of the implants.

Computer Graphics↗
PubMed2002

Influenza pandemic: preparedness planning in Germany.

The following conceptual framework formed the basis for a common decision made by the health ministers of Germany's 16 federal states to set up an influenza pandemic preparedness plan. The worst case scenario was used, on the basis of the data from the pandemic of 'Spanish flu', in 1918-20. The priority groups for vaccination were assessed, as well as the potentially available antiviral treatments. National policies could be highly improved by a common European view.

Disease Outbreaks↗
PubMed2001

The [2+2]-photocycloaddition of aromatic aldehydes and ketones to 3,4-dihydro-2-pyridones: regioselectivity, diastereoselectivity, and reductive ring opening of the product oxetanes.

3,4-Dihydro-2-pyridones [3,4-Dihydropyridin-2(1H)-ones] 6 were evaluated with respect to their use as alkene components in stereoselective Paternò-Büchi reactions. The parent compound 6a was shown to be a versatile synthetic building block that reacted with various photoexcited aromatic carbonyl compounds (benzaldehyde, benzophenone, acetophenone, methyl phenylglyoxylate, 3-pivaloyloxybenzaldehyde) with high regio- and diastereo-selectivity (51-63% yield). The products can be subjected to hydrogenolysis, opening a new and efficient route for the synthesis of 2-arylmethyl-3-piperidinols. As examples, the oxetanes 7a and 8a were hydrogenolytically cleaved and yielded the products 12 (88%) and 13 (93%). The ability of compound 6a to bind to a chiral lactam host through two hydrogen bonds was used favorably to differentiate the enantiotopic faces of its double bond. In the photocycloaddition to the chiral aldehyde 15, which was conducted at -10 degrees C in toluene, a high facial diastereoselectivity (>90% de. 56% yield) was recorded. The stereoselectivity results from a 1:1 association of dihydropyridone 6a to the aldehyde. The 4-substituted dihydropyridones 6b-6d (R = methyl, isopropyl, phenyl) were found to be less suited for potential use in photochemistry. The yields and facial diastereoselectivities recorded in their photocycloaddition to benzophenone remained low.

Aldehydes↗
PubMed2001

Enantioselective photochemical reactions of 2-pyridones in solution.

[reaction: see text] Two key photochemical reactions of prochiral 2-pyridones were studied in the presence of a chiral host. The [4 + 4]-photocycloaddition with cyclopentadiene (CpH) proceeded smoothly and with high enantioselectivity (84-87% ee). The absolute configuration of the endo-diastereoisomer was established by X-ray crystallography. The electrocyclic [4pi]-ring closure to 3-oxo-2-azabicyclo[2.2.0]-5-hexenes occurred with lower enantioselectivity (20-23% ee at -20 degrees C). The velocity of the latter reaction slowed significantly with decreasing temperature.

Journal Article↗
PubMed2001

Influence of heavy metals on the accumulation of trimethylglycine, putrescine and spermine in food plants.

Increased contents of cadmium (Cd), lead (Pb), zinc (Zn) and other heavy metals in barley plants enhanced the accumulation of trimethylglycine (betaine), putrescine and spermine. Higher contents of heavy metals in barley were caused by soil enrichment with heavy metals and by soil salinity. The highest accumulation of spermine and betaine (increase 3-fold or 5-fold in comparison to untreated soil substrates) was obtained at the highest concentration of heavy metals in plants. Consequently the betaine-N/protein-N-ratio and the spermine-N/protein-N-quotient increased 3-fold in plants with high heavy metal contents. The biomass formation was not changed significantly by the different experimental treatments.

Betaine↗
PubMed2001

[A testing device for quality assurance of 3D-ultrasound equipment].

A test object for 3D-ultrasound (US) imaging equipment was constructed, that could be used for various purposes: For training of the correct technical setup procedures and practical handling of a 3D-US equipment, as well as for various quality assurance procedures. The size and volume of these structures were known precisely (+/- 0.1 mm resp. +/- 0.06 mL, respectively; smallest volume: 0.1 mL). The stability of the structures was in agreement with guideline IEC 854 and allowed to quantify exactly the imaging and measurement errors of size and volume measurements performed with commercial 3D-equipment. The test object is well suited to validate measured volume data, as well as to perform procedures of technical quality assurance in a reproducible manner.

Guidelines as Topic↗
PubMed2001

[Analysis of the convergence relation of reconstructed algorithms disregarding local and global visual evaluations].

Tomographic reconstruction methods used in positron emission tomography are classified in two major groups: the traditionally and still widely applied filtered backprojection, and the iterative methods based on statistical models. This study focused on the objective comparison of different reconstruction algorithms, excluding criteria based on pure visual evaluation. The evaluation criteria were mathematically defined parameters, i.e., mean square error, standard deviation, signal-to-noise ratio and contrast recovery. The methods used for comparison were the classical filtered backprojection, the maximum likelihood expectation maximization algorithm, the maximum a-posteriori reconstruction model based on the Bayes Theorem, as well as the acceleration algorithms based on ordered subsets and high over-relaxation. These algorithms were evaluated by means of a mathematical brain phantom and of a physical spherical phantom. In terms of the applied parameters, the majority of the experiments showed a quantifiable superiority of the iterative methods compared the filtered backprojection.

Algorithms↗
PubMed2001

Local calibrated bone mineral density in the mandible presented using a color coding scheme.

Calibrated information on bone mineral density (BMD) may be used in dental implantology to measure "bone quality". It can be used to estimate the expected primary implant stability preoperatively and to guide the surgeon in selecting optimum implant types and operation techniques. Using a preoperative dental computed tomography (Dental-CT) scan, all of this information can be obtained without additional examinations and thus without additional X-ray exposure of the patient. In contrast to bone mineral determination in other body regions, local BMD values are important in the jaw bone. Therefore, a regimen where color-coded information on local bone mineralization is superimposed on Dental-CT images is proposed using the original CT volumes as well as reformatted views.

Bone Density↗
PubMed2001

In-vitro assessment of a registration protocol for image guided implant dentistry.

In this study a computer aided navigation technique for accurate positioning of oral implants was assessed. An optical tracking system with specially designed tools for monitoring the position of surgical instruments relative to the patient was used to register 5 partially or completely edentulous jaw models. Besides the accuracy of the tracking system, the precision of localizing a specific position on 3-dimensional preoperative imagery is governed by the registration algorithm which conveys the coordinate system of the preoperative computed tomography (CT) scan to the actual patient position. Two different point-to-point registration algorithms were compared for their suitability for this application. The accuracy was determined separately for the localization error of the position measurement hardware (fiducial localization error-FLE) and the error as reported by the registration algorithm (fiducial registration error-FRE). The overall error of the navigation procedure was determined as the localization error of additional landmarks (steel spheres, 0.5 mm diameter) after registration (target registration error-TRE). Images of the jaw models were obtained using a high resolution CT scan (1.5 mm slice thickness, 1 mm table feed, incremental scanning, 120 kV, 150 mAs, 512 x 512 matrix, FOV 120 mm). The accuracy of the position measurement probes was 0.69 +/- 0.15 mm (FLE). Using 3 implanted fiducial markers, FRE was 0.71 +/- 0.12 mm on average and 1.00 +/- 0.13 mm maximum. TRE was found to be 1.23 +/- 0.28 mm average and 1.87 +/- 0.47 mm maximum. Increasing the number of fiducial markers to a total of 5 did not significantly improve precision. Furthermore it was found that a registration algorithm based on solving an eigenvalue problem is the superior approach for point-to-point matching in terms of mathematical stability. The experimental results indicate that positioning accuracy of oral implants may benefit from computer aided intraoperative navigation. The accuracy achieved compares well to the resolution of the CT scan used. Further development of point-to-point/point-to-surface registration methods and tracking hardware has the potential to improve the precision of the method even further. Our system has potential to reduce the intraoperative risk of causing damage to critical anatomic structures, to minimize the efforts in prosthetic modelling, and to simplify the task of transferring preoperative planning data precisely to the operating room in general.

Algorithms↗